Optoelectronic semiconductor chips comprising wavelength conversion substances are described in the document WO 97/50132, for example. This document proposes applying the wavelength conversion substance to the radiation-emitting semiconductor body for example in the form of a layer embodied over a whole surface. The wavelength conversion substance of the layer converts part of the radiation emitted by the semiconductor body into radiation of other wavelengths, such that the semiconductor chip emits mixed-colored radiation, for example visible white light. Furthermore, said document also describes using not just one wavelength conversion substance but two wavelength conversion substances, for example in order to be able to better set the chromaticity coordinate of the radiation emitted by the semiconductor chip.
With the use of two or more wavelength conversion substances in conjunction with optoelectronic semiconductor bodies, however, mutual absorption can occur. If the semiconductor body emits for example radiation from the blue spectral range, which is converted partly into radiation from the red spectral range by a first wavelength conversion substance and partly into radiation from the green spectral range by a different, second wavelength conversion substance, then the radiation converted into radiation from the green spectral range by the second wavelength conversion substance can be absorbed by the second, red emitting wavelength conversion substance. This increases the internal losses of the optoelectronic semiconductor chip and thus reduces the efficiency thereof. Furthermore, the absorption of electromagnetic radiation by wavelength conversion substances is generally wavelength-selective, whereby an undesired shift in the emission spectrum of the semiconductor chip generally occurs in the case of the effect described above.
If only one wavelength conversion substance is used, then thickness fluctuations of the wavelength-converting layer generally occur on account of the limited metering accuracy. However, deviations in the thickness of the wavelength-converting layer of a few micrometers already considerably change the chromaticity coordinate of the radiation emitted by the optoelectronic semiconductor chip. Producing reproducible layer thicknesses over the entire chip area furthermore requires a high manufacturing outlay.